Natural Gas used in Agriculture

Will Natural Gas Fuel America in the 21st Century?

May 2011    Post Carbon Institute

Agriculture and Natural Gas by Michael Bomford

Michael Bomford is a research scientist and extension specialist at Kentucky State University and an adjunct faculty member in the University of Kentucky Department of Horticulture. His work focuses on organic and sustainable agriculture systems suitable for adoption by small farms operating with limited resources.

Natural gas has many uses in the agricultural sector, both on-farm and off-farm; it has provided between a third to half of the fossil fuel energy used by U.S. farms over the past 40 years.1

The vast majority of the natural gas supporting American agriculture today is used off-farm. Most of it is used to manufacture farm inputs like pesticides, plastics, and fertilizers; nitrogen fertilizer production in turn accounts for most of that. Nitrogen fertilizer use has almost quadrupled in the U.S. since 1961 while rising more than eight-fold globally (Figure 1); industrial production of nitrogen fertilizer accounts for 2-3% of natural gas consumption in the U.S., and about 5% globally.2 A less significant use of natural gas off-farm is the generation of electricity for farms, even though electricity consumption rose from 6% of farm energy use in 1965 to 22% in 2002.3

The least significant use of natural gas in the farming sector is on-farm, where it is used primarily for energy: powering irrigation pumps, drying crops before storage, heating buildings and greenhouses, and other uses. Efficiency gains and fuel substitution enabled American farmers to cut on-farm use of natural gas from 8% of U.S. farm energy use in 1965 to 4% in 2002.

Nitrogen Fertilizer Production

Nitrogen is the most abundant element in the earth’s atmosphere and the most important mineral nutrient for crop production. Plants need nitrogen to make proteins, but they cannot access the nitrogen in the air because it consists mainly of stable pairs of nitrogen atoms bound together by strong chemical bonds. Nitrogen fertilizer is made by combining gaseous nitrogen (N2) and hydrogen (H2) under very high heat and pressure to form ammonia (NH3). Nitrogen gas comes from the air and natural gas typically provides both the hydrogen and the energy needed to maintain the temperature and pressure that enables the reaction. Although ammonia can be used to make plastics, synthetic fibers, resins, explosives, fuels, and other chemical compounds, almost 90% of it is currently used for fertilizer.

Nitrogen fertilizer production in the U.S. fell by one third between 1995 and 2010, while imports rose from 15% to 43% of consumption.10 The imported fertilizer is made in countries with plentiful natural gas, including Trinidad and Tobago (57%), Russia (15%), Canada (13%), the Ukraine (7%), and others (8%). As a result, regions that use nitrogen fertilizer may be far removed from the regions that bear the environmental costs of its production.

Chemical Dependence?

The rapid increase in nitrogen fertilizer consumption in the latter half of the 20th century is often credited with keeping grain production growing faster than population. President Nixon’s secretary of agriculture, Earl Butz, famously dismissed the idea of large-scale conversion to organic methods (which preclude the use of synthetic nitrogen fertilizer) by saying, “Before we move in that direction we must decide which 50 million of our people will starve.”14 A quarter century later, geographer Vaclav Smil estimated that “at least two billion people are alive because the proteins in their bodies are built with nitrogen that came—via plant and animal foods—from a factory […] In just one lifetime,” he concluded, “humanity has indeed developed a profound chemical dependence.”

[Bomford then goes on to explain how we could use less nitrogen and the benefits that would have, and believes organic agriculture can grow as much food].


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